JP2020017230A - Control apparatus, control method and computer program - Google Patents

Abstract

To provide a control apparatus, a control method and a computer program that can set an appropriate amount of operation, in accordance with a change of a control target.SOLUTION: A control apparatus according to a present embodiment has a bias generation unit and an extreme value control unit. The bias generation unit applies a bias to the amplitude of a perturbation signal. The extreme value control unit adds the perturbation signal with the bias applied thereto, to an amount of operation applied to a control target process and applies the amount of operation to a predetermined evaluation function, thereby acquiring an evaluation function value indicating an index relating to the optimization of the control target process, and searching for an optimum value for the amount of operation applied to the control target process on the basis of the evaluation function value.SELECTED DRAWING: Figure 1

Description

  Embodiments of the present invention relate to a control device, a control method, and a computer program.

  In recent years, as a method of plant control, a technique called extreme value control has attracted attention. Extreme value control is a control technique capable of searching for an optimum value of an operation amount in real time without using a complicated model that simulates a plant. The outline of the extreme value control is based on a control amount based on a control amount of a control target process generated by forcibly changing an operation amount given to a process to be controlled (hereinafter, referred to as a “control target process”). This is to search for an operation amount at which the evaluation amount becomes an optimum value. When such extreme value control is applied to plant control, it is necessary to set various parameters related to extreme value control (hereinafter, referred to as “control parameters”). Conventionally, some guidelines for appropriately setting control parameters according to the characteristics of a process to be controlled have been proposed. However, when a system in which there are a plurality of points (extreme values) at which the evaluation function value is locally minimum or maximum is applied to extreme value control employing a control parameter setting method based on a conventional guideline, In some cases, it may be difficult to appropriately search for an operation amount at which the evaluation function value becomes the minimum or maximum (optimum value) in the entire system.

JP 2017-224176 A JP-A-9-274506 JP 2012-141862 A

  An object of the present invention is to provide a control device, a control method, and a computer program that can set an appropriate operation amount according to a change in a control target.

  The control device according to the embodiment has a bias generation unit and an extreme value control unit. The bias generator adds a bias to the amplitude of the perturbation signal. The extreme value control unit adds the biased perturbation signal to the manipulated variable given to the control target process, and gives the manipulated variable to a predetermined evaluation function to thereby provide an evaluation indicating an index related to optimization of the control target process. A function value is acquired, and an optimum value of the manipulated variable given to the control target process is searched based on the evaluation function value.

FIG. 4 is a block diagram illustrating an operation example of extreme value control according to the embodiment. FIG. 6 is a diagram illustrating a specific example of a position where extreme value control is applied to an evaluation function having a plurality of extreme values in the embodiment. FIG. 3 is a block diagram for adding a bias to a first dither signal according to the embodiment. FIG. 6 is a diagram illustrating a first specific example of a search for an evaluation function value according to the embodiment. FIG. 4 is a block diagram for setting an amplitude to a first dither signal according to the embodiment. FIG. 6 is a diagram illustrating a second specific example of searching for an evaluation function value according to the embodiment. The figure showing the outline of the water treatment plant to which the embodiment is applied. FIG. 2 is a functional block diagram illustrating a specific example of a functional configuration of the control device according to the first embodiment. FIG. 3 is a diagram illustrating a specific example of extreme value control based on the control device according to the first embodiment. FIG. 6 is a diagram illustrating a specific example of a temporal change of an operation amount and an evaluation function value in the extreme value control according to the first embodiment. FIG. 9 is a functional block diagram illustrating a first specific example of a functional configuration of a control device according to a second embodiment. FIG. 9 is a functional block diagram illustrating a second specific example of the functional configuration of the control device according to the second embodiment. FIG. 10 is a diagram illustrating a specific example of a temporal change of an operation amount and an evaluation function value in the extreme value control according to the second embodiment. FIG. 13 is a functional block diagram illustrating a specific example of a functional configuration of a control device according to a third embodiment.

  Hereinafter, a control device, a control method, and a computer program of an embodiment will be described with reference to the drawings.

(First embodiment)
[Overview]
Extreme value control is a control method for adaptively searching for the optimal value of the evaluation function based on the operation amount of the control target process and a change in the evaluation function value according to the change in the operation amount. The evaluation function value is determined based on the operation amount of the process to be controlled. The evaluation function value is a value indicating an index related to optimization of the process to be controlled. The relationship between the evaluation function value and the operation amount is represented by a predetermined evaluation function. The evaluation function may be set based on any evaluation criteria as long as it is based on the operation amount. The evaluation function value may be the operation amount itself. Generally, in a control target process in extreme value control, this evaluation function is an unknown function with respect to an operation amount.

  In general, in the extreme value control, the operation amount is forcibly vibrated by applying a dither signal, and an evaluation function value that changes according to the operation amount is observed. Then, the operation amount is changed in such a direction that the evaluation function value approaches the optimum value of the evaluation function. The method of making the evaluation function value closer to the optimum value of the evaluation function by repeatedly increasing and decreasing the operation amount is a concept of the process control by the extreme value control. The dither signal acting on the operation amount is often given as a sine wave.

  FIG. 1 is a block diagram illustrating an operation example of the extreme value control according to the embodiment. FIG. 1 shows a plant 100 which is a process to be controlled, and an extreme value control system 200 that realizes extreme value control of the plant 100. The extremum control system 200 realizes the extremum control of the plant 100 by repeating the following processing flow.

  The manipulated variable u output from the extreme value control system 200 is input to the plant 100 (Step S101). Hereinafter, for simplicity, the operation amount u input in step S101 is referred to as a first operation amount. The plant 100 outputs the evaluation function value y as a response to the first manipulated variable (Step S102). Hereinafter, for the sake of simplicity, the evaluation function value y input in step S102 is referred to as a first evaluation function value. The evaluation function value y is input to the extreme value control system 200.

  The extreme value control system 200 determines a second operation amount that brings the evaluation function value closer to an optimal value based on the first evaluation function value. The extreme value control system 200 outputs the second operation amount determined based on the first evaluation amount to the plant 100 as a new operation amount (Step S103). The plant 100 outputs a second evaluation function value as a response to the second manipulated variable (Step S104).

  By such a processing flow, the second evaluation function value is closer to the optimum value than the first evaluation function value. In the extreme value control, the calculation of the evaluation function value based on the operation amount and the determination of a new operation amount based on the evaluation function value are repeatedly executed, so that the evaluation function value converges to the optimum value. The operation amount of the plant 100 is controlled as described above.

  The function of determining the second operation amount based on the first evaluation function value is realized by the following configuration of the extreme value control system 200. The extreme value control system 200 includes a high-pass filter 201 (HPF: High-Pass Filter), a dither signal output unit 202, a multiplier 203, a low-pass filter 204 (LPF: Low-Pass Filter), an integrator 205, an adder 206, and an amplitude. A setting unit 207 is provided. In FIG. 1, s denotes a Laplace operator, ω denotes an angular frequency of a dither signal, a denotes an amplitude of the dither signal, and k denotes an integration coefficient of the integrator 205.

  The high-pass filter 201 receives the feedback signal of the evaluation function value and removes a constant bias from the signal of the evaluation function value in accordance with the minimum value. The high-pass filter 201 outputs to the multiplier 203 a signal of the evaluation function value from which the bias has been removed.

  The dither signal output unit 202 outputs a dither signal to the multiplier 203 and the adder 206. The dither signal output unit 202 outputs a first dither signal represented by sinωt to an adder 206 by a dither signal output unit 202-1 and a multiplier 203 by sinωt (t is a variable representing time). And a dither signal output unit 202-2 that outputs a represented second dither signal. The first dither signal corresponds to a perturbation signal added to the operation amount. The first dither signal is multiplied by a as an amplitude value by the amplitude setting unit 207 and output to the adder 206. The second dither signal serves to extract a component of the dither signal from the evaluation function value. Note that sin ωt (sine wave) is an example of a dither signal, and the dither signal may have any shape as long as it is a periodic signal.

  The multiplier 203 multiplies the signal of the evaluation function value, from which the bias has been removed, output from the high-pass filter 201 by a second dither signal. The multiplier 203 outputs a signal of the evaluation function value multiplied by the second dither signal to the low-pass filter 204.

  The low-pass filter 204 extracts a low-frequency component from the evaluation function value signal multiplied by the dither signal. The low-pass filter 204 outputs a signal indicating a low-frequency component of the signal of the evaluation function value to the integrator 205. It is considered that the low frequency component of the signal of the evaluation function value represents the frequency component of the signal of the evaluation function value changed according to the vibration of the dither signal. Therefore, it can be determined from the low frequency component of the signal of the evaluation function value whether the evaluation function value has increased or decreased with respect to the change in the operation amount.

  The integrator 205 functions as an estimator that estimates the direction of the operation amount to be moved to bring the evaluation function value closer to the optimum value, based on the low-frequency component of the signal of the evaluation function value output from the low-pass filter 204. Specifically, the integrator 205 integrates the low frequency component of the signal of the evaluation function value, and outputs an integrated signal of the low frequency component. The output integrated signal gives a direction (increase direction or decrease direction) to be moved with respect to the current operation amount.

  The adder 206 generates an operation amount signal to be input next to the plant 100 based on the current operation amount signal and the integration signal output from the integrator 205. The adder 206 adds a first dither signal (a × sinωt) for vibrating the operation amount signal to the generated operation amount signal, and outputs the sum to the plant 100.

  Among the functions provided in the extreme value control system 200, the first dither signal that plays a role in giving vibration to the operation amount is a function that affects the performance of searching for the optimum value of the evaluation function. In particular, when the evaluation function is special, there is a possibility that sufficient optimum value search performance cannot be exhibited. In general, a sine wave is used for the first dither signal. The amplitude a, which is a parameter of the first dither signal, may be set within a range of the manipulated variable (for example, within a range restricted by the operating conditions of the plant 100).

FIG. 2 is a diagram illustrating a specific example of the position where the extreme value control is applied to the evaluation function having a plurality of extreme values according to the embodiment. Extreme the control system 200 may converge to the first extreme value when performing the search as is increased gradually manipulated variable from an initial value U _alpha operation amount. Also, the extreme value control system 200 may converge to the second extreme Doing search to continue to reduce gradually the operation amount from the operation amount initial value U _beta. That is, the extreme value control system 200 captures a change in the evaluation function value in the vicinity of the second extreme value where the evaluation function value is smaller than the first extreme value even when the operation amount is given by the set dither signal. It is assumed that there may be cases where it is not possible.

  In order to solve such a problem, the control device of the embodiment has the following two functions. One is a function of adding a bias signal to the first dither signal. Another function is to change the amplitude a of the first dither signal over time. With such a function, the control device of the embodiment can maintain the operation amount at an appropriate value.

[Details of the first function]
FIG. 3 is a block diagram for adding a bias to the first dither signal according to the embodiment. The extreme value control system 200a in FIG. 3 differs from the extreme value control system 200 in further including a bias generation unit 208, but the other configuration is the same. Hereinafter, differences from the extreme value control system 200 will be described.

  The bias generator 208 adds a positive or negative bias to the amplitude of the first dither signal. For example, the bias generator 208 may add a bias to the first dither signal by outputting a rectangular wave signal such as a Rect function to the adder 206. Note that the magnitude of the bias may be set so as to comply with the constraint on the operation amount. The constraints may be specified in advance by the user. The user may be, for example, an operator of the plant 100 or any person. The bias generation unit 208 may be driven so as to stop adding a bias to the first dither signal when the extreme value cannot be searched for the reason that the bias reaches the limit value of the constraint condition. . The bias generation unit 208 may arbitrarily change the method of adding a bias. The bias generation unit 208 may receive a constraint condition of the plant. For example, the bias generator 208 may accept a constraint condition so as to add a positive or negative one-way bias. The bias generator 208 may use an arbitrary waveform as the bias signal to be added, not limited to a rectangular wave, and may use an irregular signal that is not periodic. When it takes time for a sudden change in the operation amount to be reflected on the plant due to the characteristics of the plant, the bias generation unit 208 may synchronize the change with the time at which the change can be captured.

By applying extreme control system 200a to the evaluation function of Fig. 2, the case where to start the search from the initial operating amount U _alpha. FIG. 4 is a diagram illustrating a first specific example of searching for an evaluation function value according to the embodiment. FIG. 4A shows a time-series change of the first dither signal. FIG. 4B shows a time-series change of the operation amount. FIG. 4C shows a time-series change of the evaluation function value.

As shown in FIG. 4 (b), immediately after starting the operation amount approaches at a constant rate to the manipulated variable U ₁ of the first extremum. Thereafter, the manipulated variable reaches U ₁ and stabilizes. This is when the search is started from the operation amount U _alpha, a behavior due to the action of extreme control techniques more evaluation function value than the evaluation function value of the start point is gradually changing the operation amount in a direction to reduce. However, once the operation amount when it reaches the U _1, because that part is viewed locally "optimum point", the control is stabilized. Therefore, it may be difficult to reach the operation amount of the second extreme value having a lower evaluation function value.

Since the extreme value control system 200a includes the bias generation unit 208, a positive or negative bias is added to the first dither signal, and the dither signal can be forcibly shifted to the positive or negative side. Thereby, the behavior of the operation amount shifts to the negative side or the positive side, and thus the extreme value control system 200a can expand the search range. Accordingly, the extreme value control system 200a can find a region having a lower evaluation function value. Extreme control system 200a may search a manipulated variable U ₂ the evaluation function value than the first extremum is lower second extreme.

[Details of second function]
FIG. 5 is a block diagram for setting an amplitude to the first dither signal according to the embodiment. The extremum control system 200b in FIG. 5 differs from the extremum control system 200 in further including an amplitude determination unit 209 and a multiplier 210, but the other configuration is the same. Hereinafter, differences from the extreme value control system 200 will be described.

  The amplitude determiner 209 determines the amplitude a set for the first dither signal. The amplitude determiner 209 changes the amplitude a of the first dither signal over time. For example, the amplitude determining unit 209 may determine the amplitude a such that the amplitude of the first dither signal increases linearly. The upper limit of the amplitude a may be set in advance in consideration of the upper and lower limits of the value of the manipulated variable, the upper and lower limits of the rate of change, or the constraints of the plant. The initial value or the increasing function of the amplitude a may be set arbitrarily.

By applying extreme control system 200b to the evaluation function of Fig. 2, the case where to start the search from the initial operating amount U _alpha. FIG. 6 is a diagram illustrating a second specific example of the search for the evaluation function value according to the embodiment. FIG. 4 (6) shows a time-series change in the amplitude of the first dither signal. FIG. 6B shows a time-series change of the operation amount. FIG. 6C shows a time-series change of the evaluation function value.

As shown in FIG. 6A, the amplitude of the first dither signal gradually increases, and the extreme value control system 200b can expand the search range of the operation amount. If the initial value of the manipulated variable and U _alpha, extreme control system 200b is immediately after the search started, the amplitude of the first dither signal is small, the behavior to stabilize at operating amount U ₁ of the first extremum Show. However, the variation width of the operation amount is further increased to reach the operating amount U ₂ of the second extremum. As described above, the extreme value control system 200b can further reduce the evaluation function value, and can search for the optimum value.

  The first function and the second function may be combined with each other to form an extreme value control system. By being combined, the extreme value control system can more stably search for the optimum value.

  FIG. 7 is a diagram schematically illustrating a water treatment plant 300 to which the embodiment is applied. The process to be controlled is not limited to the water treatment plant 300, and may be any process having an evaluation function value to be optimized. Hereinafter, the function of the real-time optimum value search control device will be described in detail by taking the water treatment plant 300 that realizes the biological wastewater treatment process as an example. The water treatment plant 300 is one aspect of a process to be controlled.

  The white arrow in FIG. 7 represents the flow of the sewage to be treated. The solid arrow in FIG. 7 represents the flow of the sludge separated from the sewage. The outline of the water treatment plant 300 will be described. The water treatment plant 300 includes respective storage facilities such as an inflow culvert / sand basin 301, a first sedimentation basin 302, a biological reaction tank 303, a final sedimentation basin 304, a filtration pond 305, and an excess sludge storage tank 307. Further, the water treatment plant 300 includes a sludge treatment pump 308, a sludge extraction pump 321, a blower 331, an excess sludge extraction pump 341 and a return sludge pump 342. The sludge extraction pump 321 delivers the water to be treated or the sludge between the storage facilities. The blower 331 aerates sewage in the biological reaction tank 303. The excess sludge extraction pump 341 is a pump that extracts excess sludge from the final sedimentation basin 304. The sludge extracted by the excess sludge extraction pump 341 is stored in the excess sludge storage tank 307 together with the sludge initially extracted by the sedimentation basin 302. The sludge stored in the excess sludge storage tank 307 is carried by the sludge treatment pump 308 and processed. The inflowing sewage flows along the white arrow in FIG. 7 and is discharged through an inflow culvert / sand basin 301, a first sedimentation basin 302, a biological reaction tank 303, a final sedimentation basin 304, and a filtration pond 305.

  The sewage flowing through the inflow culvert / sand basin 301 is initially stored in the sedimentation basin 302. In the first settling basin 302, unnecessary substances having a relatively large specific gravity settle down due to gravity and settle. Sludge that has first settled in the sedimentation basin 302 is drawn out by the sludge drawing pump 321 and sent to the surplus sludge storage tank 307. On the other hand, the supernatant water to be treated is sent to the biological reaction tank 303.

  In the biological reaction tank 303, microorganisms are put into sewage. The microorganisms introduced into the sewage are activated by the aeration of the sewage by the blower 331 to decompose organic substances in the sewage, remove phosphorus in the sewage, nitrify ammonia, and remove nitrogen. By the action of microorganisms, nitrogen and phosphorus components are separated from sewage. The water to be treated that has passed through the biological reaction tank 303 is sent to the final sedimentation basin 304.

  In the final sedimentation basin 304, the activated sludge in the sewage sediments by gravity and settles. The activated sludge settled in the final sedimentation basin 304 is drawn out by the surplus sludge drawing pump 341 and sent to the surplus sludge storage tank 307. Here, a part of the activated sludge is returned to the biological reaction tank 303 by the return sludge pump 342, and is reused to promote the reaction in the biological reaction tank. On the other hand, the supernatant sewage is sent to the filtration pond 305.

  In the filtration pond 305, a final-stage purification treatment for sewage is performed, such as removal and disinfection of small unnecessary substances by filtration. The sewage that has undergone the purification treatment in the filtration pond 305 is discharged to a river or the like as treated water.

  The surplus sludge storage tank 307 is a facility for temporarily storing unnecessary sludge generated in the biological wastewater treatment process. The sludge stored in the excess sludge storage tank 307 is delivered to the sludge treatment step by the sludge treatment pump 308.

  In such a biological wastewater treatment process, the manipulated variable is the aeration air volume of the returned sludge, and the controlled variable is the concentration of nitrogen and phosphorus contained in the effluent (hereinafter referred to as “discharged nitrogen concentration” and “discharged phosphorus concentration”, respectively). It is.) The discharged nitrogen concentration and discharged phosphorus concentration are measured after passing through a filter pond disinfection facility. The control amounts may be the amounts of nitrogen and phosphorus contained in the discharge water (hereinafter, referred to as “discharge nitrogen amount” and “discharge phosphorus amount”, respectively). In this case, the discharged nitrogen amount and the discharged phosphorus amount are obtained by multiplying the discharged nitrogen concentration and the discharged phosphorus concentration by the discharged flow amount, respectively.

  The evaluation function described in FIG. 7 defines an unknown value for the operation amount as a function of the control amount. In the case of FIG. 7, the evaluation function is a function representing the relationship between the discharged nitrogen concentration and the discharged phosphorus concentration and the evaluation amount. The evaluation function is set to take an extreme value between the control amount at the upper limit of the operation amount (aeration air amount) and the control amount at the lower limit of the operation amount. As an example of a method of setting the evaluation function, the sum of the water quality cost, the power cost of the return sludge pump 342, and the power cost of the blower 331 (hereinafter, referred to as “total cost”) is based on the concept of a drainage charge. There is a method of expressing as.

  The power cost of the returned sludge pump 342 and the blower 331 can be calculated from the returned sludge flow rate and the rated power of the returned sludge pump 342 and the blower 331. It is known that those that greatly change by changing the return rate or the blower 331 are the nitrogen concentration and the phosphorus concentration. Therefore, the water quality cost is expressed by the following equation (1), where TN is the discharged nitrogen and TP is the discharged phosphorus.

  It should be noted that increasing the amount of aeration air increases the nitrogen removal rate, thereby reducing the water quality cost related to TN. On the other hand, when the amount of aeration air is reduced, the removal rate of phosphorus increases, so that the water quality cost related to TP decreases. In such a case, the evaluation function may be set based on the water quality cost. However, when the cost of water qualities that do not have a trade-off relationship, such as phosphorus and nitrogen, is used as an index, the evaluation function is expressed as the total cost that includes the operation cost (electric power cost) and the evaluation amount. An extreme value is set between the control amount at the upper limit of the amount (aeration air amount) and the control amount at the lower limit of the operation amount.

  Further, a constraint condition that satisfies the discharge water quality constraint may be incorporated in the evaluation function. For example, a regulation value for the discharge water quality is provided, and a function that increases the total cost when the regulation value is exceeded is incorporated. When such an evaluation function is used, the evaluation amount sharply increases when the evaluation value exceeds the regulation value. Therefore, it can be expected that the extreme value control functions so as to suppress the evaluation amount within the regulation value.

  The period of the first dither signal corresponding to the perturbation signal added to the manipulated variable and the period of the second dither signal serving to extract the dither signal component from the evaluation function value are set sufficiently later than the time constant of the plant. Accordingly, a change in the evaluation function can be grasped by a change in the operation amount accompanying the dither signal.

  Although the application example of the extreme value control in the water treatment plant 300 has been described above, the process to be subjected to the extreme value control is not limited to the biological wastewater treatment process. Extreme value control is applicable to any process that has a metric to be optimized.

  FIG. 8 is a functional block diagram illustrating a specific example of a functional configuration of the control device 1 according to the first embodiment. The control device 1 includes a CPU (Central Processing Unit), a memory, and an auxiliary storage device connected by a bus, and executes a control program. The control device 1 functions as a device including the extreme value control unit 20, the bias generation unit 208, and the bias adjustment unit 211 by executing the control program. Note that all or a part of each function of the control device 1 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), and an FPGA (Field Programmable Gate Array). The control program may be recorded on a computer-readable recording medium. The computer-readable recording medium is, for example, a portable medium such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and a storage device such as a hard disk built in a computer system. The control program may be transmitted via a telecommunication line.

  The extreme value control unit 20 of the control device 1 outputs an operation amount that brings the evaluation function value closer to the optimum value based on the input evaluation function value. Such a function of the extreme value control unit 20 is realized by including a configuration similar to that of the extreme value control system 200a illustrated in FIG. Therefore, the same reference numerals as those in FIG. 3 denote the same components, and a description of a configuration equivalent to that of the extreme value control system 200a will be omitted.

  The bias adjuster 211 controls the bias applied by the bias generator 208. For example, the bias adjustment unit 211 sets the magnitude of the bias such that the magnitude of the operation amount signal to which the bias is added is less than the upper limit of the aeration air volume. The bias adjustment unit 211 outputs to the bias generation unit 208 an instruction to stop generation of a bias or timing of generation of a bias to the dither signal. The bias adjustment unit 211 receives the evaluation function value as an input, calculates a period average of the evaluation function value, keeps a history of the calculation result, and compares the period average value before and after the bias. The bias adjustment unit 211 outputs an instruction to stop adding a bias to the first dither signal when the periodic average value of the evaluation function value does not change even when the bias is applied. When the water treatment plant 300 is in an unstable state, the bias adjustment unit 211 outputs an instruction to stop adding a bias to the first dither signal. The situation in which the water treatment plant 300 is unstable may be, for example, a situation in which the evaluation function value changes greatly or changes discontinuously in a short time. The recording timing of the cycle average of the evaluation function value of the bias adjustment unit 211 may be set arbitrarily. The recording timing may be synchronized with the frequency of the dither signal on the assumption that the water treatment plant 300 is operated stably.

  The bias adjustment unit 211 may instruct the bias generation unit 208 to apply a bias not only with a rectangular wave but with an arbitrary waveform. The bias adjusting unit 211 applies a bias with an aperiodic signal such as a probability signal or a signal synchronized with a control amount in another control target, for example, on the assumption that stable operation of the water treatment plant 300 is ensured. May be instructed. For example, in the case of the water treatment plant 300 as shown in FIG. Since the power required for water treatment and the quality of the effluent vary depending on various information such as the quality of the sewage flowing in, etc., the optimum value of the total cost may also vary. Even in such a situation, the control device 1 can be applied.

  When the behavior in which the periodic average value of the evaluation function value increases after the operation amount converges to the optimum value occurs, the bias adjustment unit 211 outputs an instruction to start adding the bias again. Note that, when the operation amount converges to the optimum place, that is, when it is confirmed that the evaluation function value becomes a constant value, the bias adjustment unit 211 outputs an instruction to stop adding a bias. The bias adjusting unit 211 confirms the increase or decrease of the evaluation function value. However, if the evaluation function value does not tend to decrease due to the addition of the bias, the evaluation function value is uniformly increased in all cases. Yes, it is determined that the optimum value has not changed, and an instruction to stop the addition of the bias is output. On the other hand, the addition of a bias may adversely affect water quality due to large fluctuations in the operation amount. Therefore, when the water quality deteriorates due to a large change in the operation amount, the bias adjustment unit 211 may stop applying the bias to return to the original water quality. In order to avoid such a situation as much as possible, the bias adjustment unit 211 may output an instruction to use a rectangular wave whose absolute value gradually increases as a function of the bias to be added.

  The control device 1 can operate the water treatment plant 300 within a range in which the regulation value of the water quality does not exceed by using the rectangular wave whose absolute value gradually increases. The bias adjustment unit 211 can also acquire the history of the value of the rectangular wave. The adjustment of the absolute value of the bias is an evaluation function value. It may be performed based on the tendency of the discharge water quality or the operation status of the control item. The bias adjustment unit 211 outputs an instruction to stop bias addition even when the water quality is deteriorated due to a factor other than the extreme value control.

  FIG. 9 is a diagram illustrating a specific example of the extreme value control based on the control device 1 of the first embodiment. In FIG. 9, the operation amount indicates the aeration air volume. In FIG. 9, the evaluation function value represents the total cost. The graph of FIG. 9 shows the relationship between the operation amount (aeration air amount) and the evaluation function value (total cost). FIG. 10 is a diagram illustrating a specific example of a temporal change of the operation amount and the evaluation function value in the extreme value control according to the first embodiment. FIG. 10A shows a temporal change of the operation amount and the evaluation function value when the extreme value control is performed by the conventional method. FIG. 10B shows a temporal change of the operation amount and the evaluation function value when the control device 1 performs the extreme value control.

  In FIG. 9, when the initial value of the operation amount is near 0, and when the extreme value control is performed by the conventional method, the operation amount converges to 0 and is stabilized as shown in FIG. On the other hand, when extreme value control is performed by the control device 1 having the configuration shown in FIG. 8, a positive bias is added to the first dither signal, so that the operation amount approaches the optimum operation amount. Thus, a behavior in which the evaluation function value converges to an operation amount (optimum value of the operation amount) that further reduces is obtained. Further, since a bias is added to the operation amount, the operation amount shifts in the increasing direction. However, the evaluation function value also increases with the bias, so that the operation amount returns due to the operation of the extreme value control. At this time, the bias adjustment unit 211 compares the periodic averages of the evaluation function values before and after adding the bias, determines that it is not necessary to add the bias next, and outputs an instruction to stop the addition of the bias. As described above, when the extreme value control in the first embodiment is applied, it is possible to search for an optimal operation amount (control parameter) even for an evaluation function having a special shape as shown in FIG.

  The control device 1 according to the first embodiment having the above-described configuration includes the bias generation unit 208 to add a positive or negative bias to the first dither signal. By adding a bias to the first dither signal, it is possible to converge to a more optimal operation amount, so that an optimal operation amount (control parameter) is searched for an evaluation function having a special shape. Can be. In addition, by providing the bias adjustment unit 211, before and after the bias is added, the cycle average of the evaluation function values is compared, and when it is determined that there is no need to add the bias, the addition of the bias is stopped. Can be. Therefore, it is possible to set and maintain an appropriate operation amount according to a change in the control target.

(Second embodiment)
FIG. 11 is a functional block diagram illustrating a first specific example of a functional configuration of the control device 1a according to the second embodiment. The control device 1a includes a CPU, a memory, an auxiliary storage device, and the like connected by a bus, and executes a control program. The control device 1a functions as a device including the extreme value control unit 20a, the amplitude determination unit 209a, and the amplitude adjustment unit 212 by executing the control program.

  The extreme value control unit 20a outputs an operation amount that brings the evaluation function value closer to the optimum value based on the input evaluation function value. Such a function of the extreme value control unit 20a is realized by including a configuration similar to that of the extreme value control system 200b illustrated in FIG. Therefore, the same reference numerals as those in FIG. 5 denote the same components, and a description of a configuration equivalent to that of the extreme value control system 200b will be omitted.

The amplitude determining unit 209a determines the amplitude a set for the first dither signal based on time. For example, the amplitude determiner 209a temporally increases the amplitude a of the first dither signal. Amplitude determining unit 209a as amplitude a of the first dither signal may be configured as a function of temporally linear increase in the rate of change a ₁ from the initial value a ₀ amplitude. Since the control device 1a includes the amplitude determination unit 209a, the amplitude a gradually increases with the passage of time, and the search range of the operation amount can be expanded. The amplitude determining unit 209a may determine the amplitude a using any function as long as the function is not limited to the linear increasing function and is a monotonic increasing function.

  The amplitude adjuster 212 outputs a signal for adjusting the amplitude of the first dither signal based on the evaluation function value. For example, even if the amplitude adjustment unit 212 stops increasing the amplitude a of the first dither signal based on the input operation amount and outputs an instruction that the amplitude a of the first dither signal is a signal having a constant value. Good. When the operation amount signal obtained by adding the first dither signal (a × sin ωt) as the output of the integrator 205 reaches the upper limit of the operation amount, the amplitude adjustment unit 212 sets the constant value without increasing the value of the amplitude a. A signal to be taken may be output. With this configuration, the amplitude adjustment unit 212 becomes unstable in response to exceeding the upper limit of the allowable operation amount in the process of increasing the amplitude of the first dither signal, thereby causing the plant response to become unstable. Can be prevented.

  FIG. 12 is a functional block diagram illustrating a second specific example of the functional configuration of the control device 1b according to the second embodiment. The control device 1b includes a CPU, a memory, an auxiliary storage device, and the like connected by a bus, and executes a control program. The control device 1b functions as a device including the extreme value control unit 20b, the amplitude determination unit 209a, and the amplitude adjustment unit 212b by executing the control program. Hereinafter, points different from the first specific example will be described.

  The control device 1b outputs an operation amount for bringing the evaluation function value closer to the optimum value based on the input evaluation function value. Such a function of the control device 1b is realized by including the same configuration as the extreme value control system 200b illustrated in FIG. Therefore, the same reference numerals as those in FIG. 5 denote the same components, and a description of a configuration equivalent to that of the extreme value control system 200b will be omitted.

  The amplitude adjustment unit 212b may output a signal that stops increasing the amplitude a of the first dither signal based on the response of the water treatment plant 300. The amplitude adjuster 212b calculates the average of the period based on the input evaluation function value. The amplitude adjustment unit 212b records the tendency of the cycle average value as a history. The amplitude adjustment unit 212b outputs an instruction to stop the increase in the amplitude a of the first dither signal when a discontinuous abnormality is found in the transition of the cycle average value. With such a configuration, the amplitude adjustment unit 212b can adjust the amplitude a in a situation where the water treatment plant 300 operates stably. In addition, in the configuration of FIG. 12, the amplitude adjustment unit 212b determines that the evaluation function value tends to decrease from the average value of the recorded evaluation function values in a situation where the water treatment plant 300 is operating stably. When it is determined that the first dither signal cannot be seen, a signal for stopping the increase of the amplitude a of the first dither signal may be output.

  The amplitude adjuster 212b may arbitrarily change the function for determining the amplitude a set in the amplitude determiner 209a during the control. For example, when there is a strict water quality regulation for a change in the operation amount in the sewage treatment control, the water treatment plant 300 performs the operation within a range not exceeding the water quality regulation. At this time, if the operation value of the aeration air volume for the blower 331 is changed, the water quality may be significantly deteriorated. The amplitude adjusting unit 212b may change the function of the amplitude a of the first dither signal little by little while acquiring the response of the water quality so as to cope with such a case. When the value of the amplitude a affects the setting guideline of the other parameter other than the amplitude a of the first dither signal, the amplitude adjuster 212b reflects the change information of the amplitude a on the other parameter. For example, when the amplitude information of the first dither signal is necessary for adjusting the integration gain KI, the amplitude adjustment unit 212b reflects the change information of the amplitude a on the integrator 205.

  An effect when the extreme value control having the configuration of the second embodiment is applied to the evaluation function shown in FIG. 9 will be described. FIG. 13 is a diagram illustrating a specific example of a temporal change of the operation amount and the evaluation function value in the extreme value control according to the second embodiment. As shown in FIG. 13, it can be seen that the amplitude of the operation amount increases as the amplitude a of the first dither signal increases. As the vibration width of the operation amount increases, the fluctuation width of the evaluation function value also increases, and it becomes possible to specify the direction in which the evaluation function value decreases. The amplitude adjustment unit 212b acquires the history of the average of the evaluation function values, determines that the value of the history of the average of the evaluation function values has not changed, and stops increasing the amplitude of the first dither signal. And outputs an instruction that the value of the amplitude a becomes a constant value signal. After the operation amount converges to the optimum value, the operation amount and the oscillation width of the evaluation function value become constant.

  The control device 1a of the second embodiment configured as described above can determine the value of the amplitude added to the first dither signal by including the amplitude determining unit 209a. Since the value of the amplitude increases with the passage of time, the search range of the operation amount can be expanded. In addition, by providing the amplitude adjustment unit 212, when the operation amount signal reaches the upper limit value of the operation amount, a signal is output so that the value of the amplitude a does not increase and takes a constant value, thereby obtaining the value of the amplitude. Can be prevented from becoming too large, and the search range of the operation amount becomes too wide. Therefore, it is possible to prevent the response of the plant from becoming unstable, and to stably operate the plant by setting and maintaining an appropriate operation amount according to a change in the plant. Further, the control device 1b of the second embodiment can arbitrarily change the function for determining the amplitude added to the first dither signal by including the amplitude adjusting unit 212b. With this configuration, the function can be changed little by little based on the evaluation function value from the plant. Therefore, even when a predetermined regulation is provided in the plant, the plant can be operated more easily without exceeding the regulation.

(Third embodiment)
The third embodiment is an embodiment in which the first embodiment and the second embodiment are combined. By adopting the third embodiment, it is possible to learn the variation of the evaluation function value accompanying a wider variation of the operation amount than in the first embodiment and the second embodiment, and to quickly search for the optimum value. Becomes possible.

  FIG. 14 is a functional block diagram illustrating a specific example of the functional configuration of the control device 1c according to the third embodiment. The control device 1c includes a CPU, a memory, an auxiliary storage device, and the like connected by a bus, and executes a control program. The control device 1c functions as a device including the extreme value control unit 20c, the bias generation unit 208, the amplitude determination unit 209a, and the amplitude adjustment unit 212c by executing the control program. Hereinafter, points different from the first embodiment and the second embodiment will be described.

  The amplitude adjustment unit 212c determines the state of the water treatment plant 300 based on the history of the periodic average value of the evaluation function value. For example, when the operation amount reaches the upper limit value or when the evaluation function value becomes abnormal, the amplitude adjustment unit 212c outputs an instruction to stop bias addition to the first dither signal to the bias generation unit 208. , Outputs an instruction to change the amplitude setting of the first dither signal to the amplitude determining unit 209a.

  The control device 1c thus configured can determine the state of the plant based on the history of the periodic average value of the evaluation function value by including the amplitude adjustment unit 212. The amplitude adjustment unit 212 can instruct the stop of the bias addition to the first dither signal or the change of the amplitude of the first dither signal in accordance with the state of the plant. Therefore, appropriate control parameters can be set according to the change of the control target, and the plant can be operated more easily and stably.

  The control device 1 in the above embodiment may be configured to include a display unit and an input unit. In this case, the display unit may output a drive waveform of the bias generation unit or the amplitude determination unit, may display a perturbation signal added to the operation amount, or may display a time series of the operation amount or the evaluation function value. The change may be displayed. The input unit receives a set value that determines the waveform of the perturbation signal. The extreme value controller may be configured to control the waveform of the perturbation signal based on the received set value (for example, the amplitude). Specifically, the extreme value control unit controls the waveform of the perturbation signal based on the received set value by outputting the received set value to the bias generation unit or the amplitude determination unit.

  The display unit is an output device such as a CRT (Cathode Ray Tube) display, a liquid crystal display, and an organic EL (Electro Luminescence) display. The display unit may be an interface for connecting the output device to the control device 1. In this case, the display unit generates a video signal from the video data and outputs the video signal to a video output device connected to the display unit.

  The input unit is configured using input devices such as a touch panel, a mouse, and a keyboard. The input unit may be an interface for connecting the input device to the control device 1. In this case, the input unit generates input data (for example, instruction information indicating an instruction to the control device 1) from an input signal input in the input device, and inputs the generated data to the control device 1.

  In the above embodiments, the extreme value control unit, the bias generation unit, the amplitude determination unit, and the amplitude adjustment unit are software function units, but may be hardware function units such as an LSI.

  According to at least one embodiment described above, by including the extreme value control unit, the bias generation unit, the amplitude determination unit, and the amplitude adjustment unit, it is possible to set an appropriate control parameter according to a change in a control target. .

  Although several embodiments of the present invention have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Control device, 1a ... Control device, 1b ... Control device, 1c ... Control device, 20 ... Extreme value control unit, 20a ... Extreme value control unit, 20b ... Extreme value control unit, 20c ... Extreme value control unit, 100 ... Plant, 200: extreme value control system, 200a: extreme value control system, 200b: extreme value control system, 201: high-pass filter, 202: dither signal output unit, 203: multiplier, 204: low-pass filter, 205: integrator, 206: adder, 207: amplitude setting unit, 208: bias generation unit, 209: amplitude determination unit, 209a: amplitude determination unit, 210: multiplier, 211: bias adjustment unit, 212: amplitude adjustment unit, 212b: amplitude adjustment Unit, 212c: amplitude adjustment unit, 300: water treatment plant

Claims (11)

A bias generator for adding a bias to the amplitude of the perturbation signal;
In addition to the operation amount given to the control target process to which the biased perturbation signal is added, to obtain an evaluation function value indicating an index related to optimization of the control target process by giving the operation amount to a predetermined evaluation function, An extreme value control unit that searches for an optimal value of the operation amount given to the control target process based on the evaluation function value,
A control device comprising:   The control device according to claim 1, further comprising: a bias adjusting unit that stops adding the bias performed by the bias generating unit according to the evaluation function value.   The control device according to claim 1, further comprising: a bias adjustment unit that causes the bias generation unit to change the value of the bias added to the perturbation signal according to a state or a control amount of the process to be controlled. An amplitude determination unit that determines the amplitude of the perturbation signal based on time,
In addition to the manipulated variable given to the control target process the amplitude determined perturbation signal, to obtain an evaluation function value indicating an index related to optimization of the control target process by giving the manipulated variable to a predetermined evaluation function, An extreme value control unit that searches for an optimal value of the operation amount given to the control target process based on the evaluation function value,
A control device comprising:   5. The control device according to claim 4, further comprising an amplitude adjustment unit that stops determining the amplitude of the perturbation signal performed by the amplitude determination unit according to the evaluation function value. 6.   5. The control device according to claim 4, further comprising an amplitude adjustment unit configured to change the function for determining the amplitude of the perturbation signal to the amplitude determination unit according to the operation amount.   The control device according to claim 4, further comprising an amplitude adjustment unit that changes the function for determining the amplitude of the perturbation signal to the amplitude determination unit based on a state or a control amount of the control target process. A bias generator for adding a bias to the perturbation signal;
An amplitude determination unit that determines the amplitude of the perturbation signal based on time,
An evaluation indicating an index related to optimization of the control target process by applying the perturbation signal to which the amplitude is determined and the bias is added to the control input to the control target process, and applying the control input to a predetermined evaluation function. An extreme value control unit that acquires a function value and searches for an optimum value of the operation amount given to the controlled process based on the evaluation function value,
A control device comprising: A display unit that displays a perturbation signal added to the operation amount;
An input unit that receives a set value that determines a waveform of the perturbation signal from a user,
Further comprising
The control device according to claim 1, wherein the extreme value control unit controls a waveform of the perturbation signal based on the set value. A bias generating step in which the controller applies a bias to the amplitude of the perturbation signal;
An evaluation function value indicating an index related to optimization of the control target process by applying a bias value to the operation amount given to the control target process to the control target process and applying the operation amount to a predetermined evaluation function; An extreme value control step of searching for an optimal value of the operation amount given to the control target process based on the evaluation function value,
A control method comprising:   A computer program for causing a computer to function as the control device according to claim 1.

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